Gold-Plated PCB-mount Sockets?

[Eeyore]

Right. I was asking about two separate problems. One was about
putting DIP ICs with tin- or solder-plated pins into sockets that had
gold plating. The other was about soldering the gold-plated pins, of
Molex gold-plated wire-to-board sockets, to PCBs.

AIUI neither of those need be problems. As long as the IC sockets 'grap' the legs
firmly. If they're the turned pin type with a kind of 'collet' entry they may be
troublesome. Who uses gold-plated sockets anyway ?

Graham

 

[Eeyore]

Thanks for the response, Graham.


"I also read somewhere that using silver-bearing 62/36/2 solder helps
to alleviate some of the problems associated with soldering to gold-
plated metals, by preventing most of the leaching of the gold during
soldering."

I don't see why it would be any better. As previously mentioned, soldering with SnPb
dissolves the thin gold and that's been normal practice for aeons.

Graham

 

[Eeyore]

The other was about soldering the gold-plated pins, of
Molex gold-plated wire-to-board sockets, to PCBs.

I just remembered. The part of the pin you solder is not normally gold-plated !
Why plate stuff that doesn't need to be ?

If concerned make sure you use that type.

Graham

 

[Eeyore]

1. For almost all receptacle-to-pin-mating situations, both socket and
pin surfaces should be made of the same metal.

I'd say *all* without reservation.

One exception seems to
be that acceptable performance can be gotten when putting a tin or tin/
lead DIP IC pin into a (round) machined or turned gold-plated socket

I rather doubt that. The contact pressure isn't high and you may see fretting
corrosion there. ICs can also 'walk' out of those sockets in instances of high
vibration or thermal cycling.

(but NOT a gold-plated "flat contact" or "leaf-spring" type of DIP
socket), although, if practical, no IC socket at all would be best.

No socket is best without a doubt. It's one less part to fail The 'leaf sping'
sockets aren't my favourite either. You want the 'tang' versions that really
grab the lead. These have the advantage of usually being the most inexpensive as
a rule too !

2. Soldering a gold-plated pin into a PCB, using tin/lead solder,
"should" be OK. But using 62/36/2 tin/lead/silver solder should be
better.

Maybe but get the headers with tin plate on the bit that gets soldered

Graham

 

[Al]

Failures occur between dissimilar metals on contact points only if there
is liquid water on the contacts. Even then nothing much would happen
except that ham-fingered guys, like me, touch the contacts while
inserting the ICs or whatever. Then you have an electrolyte that will
cause trouble from the salts on your fingers.

If the dissimilar contact points are are in a dry atmosphere and the
temperature never goes below the dew point of the enviroment, you will
probably never have a problem.

Clean and dry are the watch words.

Al

 

[John Larkin]

I'd say *all* without reservation.



I rather doubt that. The contact pressure isn't high and you may see fretting
corrosion there. ICs can also 'walk' out of those sockets in instances of high
vibration or thermal cycling.

We put eproms into gold-plated machined-pin sockets, and have never
had a problem after, rough guess, 50,000 device-years, which is 1.6
million pin-years, for an mtbf of over 14 billion hours per pin!

Isn't math fun?

I read somewhere that the gold is so thin, all it does is protect the
beryllium copper contact from tarnishing before it's used. The ic pin
scrapes off the gold going in, and likely scrapes off its own solder
or tin coating, so you wind up with some copper-copper contact.

John